Colorectal Cancer Flashcards
What are benign and malignant colorectal neoplasias called?
Benign - adenoma (always a polyp)
Malignant - Adenocarcinoma
What do all adenocarcinomas start as?
Adenomas - tubular (unlikely to contain malignant cells) - villous (high rish of developing into adenocarcinoma)
Describe the function of an oncogene
Normal - promotes cell growth and division
Mutated - causes excess cell growth and division - contributes to cancer
What is a tumour suppressor gene?
Normal - suppress cell growth and division
Mutated - allow cell growth and division
What does APC (gene) stand for?
adenomatous polyposis gene
How is a colorectal cancer described macroscopically?
polypoidal
ulcerative
annular ring around colon which can obstruct it
How are adenocarcinomas classified?
- well differentiated - intracellular mucin still present
- moderately differentiated - no intracellular mucin but still organised in glands
- poorly differentiated - no structure at all
Describe the stages of Dukes staging
A – tumour not penetrated the whole way through muscular wall
B – all the way through muscular wall
C – local lymph nodes are involved
D – distant mets
In TNM staging, describe the levels of T
T1 - submucosa only
T2 - into muscle
T3 - through muscle
T4 - adjacent structures (including peritoneum)
In TMN staging, describe the levels of N
N0 - no lymph node involvement
N1 - < 3 nodes involved
N2 - > 3 nodes involved
In TMN staging, describe the levels of M
M0 - no distant metastases
M1 – distant metastases
How does colorectal cancer spread?
Local structures
Lymphatic
Haematogenously
Transcoelomic (into peritoneal cavity)
GIve 2 routes of autosomal dominant inheritance of colorectal cancer
FAP - Mutation in APC gene
HNPCC - Mutation in DNA mismatch repair gene
What do FAP and HNPCC stand for?
FAP - Familial adenomatous polyposis
HNPCC - Hereditary non-polyposis colorectal cancer
Are there any predisposing conditions to CRC apart from the inherited ones?
Yes
Adenomatous polyps
UC
CD
What are the symptoms of colorectal cancer?
Depend where the cancer is:
Rectum – PR bleeding and tenesmus
Descending colon – pain, change in bowel habit, PR bleeding
Right side of colon – iron deficiency anaemia
What are the signs of colorectal cancer?
anaemia cachexia lymphadenopathy abdominal mass/distension hepatomegaly rectal mass Blood PR
How is CRC diagnosed?
Colonoscopy and biopsy #1 Faecal Occult Blood Testing Barium enema CT colonography Sigmoidoscopy
What % of CRC does FOBT detect?
70%
Who is FOBT not useful in?
symptomatic patients
Who is FOBT given to?
50-70yo every 2 years
How can CRC present as an emergency?
Obstruction (distension, constipation, pain, vomiting)
Bleeding
Perforation
How is CRC treated?
Surgery - primary treatment - only curative
Radiotherapy
Chemotherapy
R&C can be used before surgery to increase the success of the surgery
What surgery is available for rectal cancer?
- Abdomino-perineal excision
- Anterior resection
- local excision – removing small cancers via anal canal – not mainstay, experimental
What antigen (via blood test) is most commonly used to monitor patients with colorectal cancer?
Carcinoembryonic antigen (CEA)
Can a carcinoma of the colon cause a raised carcinoembryonic antigen (CEA)?
Yes
Is a cancer of the colon more common in the transverse colon or the sigmoid colon?
Sigmoid colon
Is the sigmoid colon or rectum more likely to be affected by cancer?
Rectum - most common site for cancers of the large bowel accounting for 45% of cancers
